The present invention relates to a machine tool, more particularly to a modular machine tool with a plurality of tools brought into an operation position in a cyclical fashion and provided with a workpiece holder and tool holders movable in various directions and controlled by NC-control.
Machine tools known as"processing centers" have been used in practice for years. Such machine tools have three operational axes (X, Y, Z) and a palet-like clamping device whereby a workpiece is brought by a palet feeder to an operation position. Capital costs are comparatively low although for simultaneous treatments of workpieces from many sides a rather great number of such processing centers have been required which had multiplied capital costs and also required a great deal of space for such processing centers.
Also known are so-called "multi-station switchboard machine tools" in which a loading station and three treatment or processing stations are required, and a workpiece arranged on a horizontal workpiece holder must be moved in a cyclical fashion between those processing stations. The workpiece holder has four chucks which are pivotable according to the treatment of a workpiece. Fourteen treatment axes are available altogether. However, capital costs are relatively high.
So-called multi-way automates with horizontal and vertical switch axes have been also known. Nineteen treatment axes are available in these automates and eighteen tools, seven chucks and eighteen stroke adjustments with seven stations are provided in such machine tools. Although setting periods are very short capital costs in such machine tools are comparable with those of multi-station switch-board machine tools.
An NC-control of all axes in such machines would make them practically too much expensive. Retooling of such multi-station automates is extremely expensive and time-consuming because, for example seven chucks are to be retooled. Also, in certain instances spindle holders must be laterally adjusted and recentered which would involve long setting periods.